1. Field of the Invention
The present invention relates to a semiconductor device comprising a semiconductor element covered with a coating film and a method for manufacturing the same, and particularly to a semiconductor device comprising a semiconductor light emitting element that is covered and a method for manufacturing the same.
2. Description of the Related Art
Methods of forming a coating film on a semiconductor element in the prior art include those that employ potting means or screen printing means. FIG. 14 is a sectional view schematically showing a process of a conventional film forming method that employs the potting means. FIG. 15 is a sectional view schematically showing a process of a conventional film forming method that employs the screen printing means. The processes will be described below with reference to these drawings.
A semiconductor device 200 is made by using the potting means. The semiconductor device 200 comprises a semiconductor element 210 mounted face down in a cavity 211 of a predetermined shape. Top face and side face of the semiconductor element 210 are covered with a coating film 212. The semiconductor element 210 is electrically connected with a lead electrode 215 that is formed integrally with the cavity 211. The semiconductor device 200 has the semiconductor element 210 that is mounted face down on the lead electrode 215 in advance. A resin 213 is dropped from a thin tube 214 onto the top face of the semiconductor element 210. Resin supply is stopped when the resin has completely covered the top face and side face of the semiconductor element 210, so as to harden the resin 214. Thus the coating film 212 is formed on the top face and side face of the semiconductor element 210.
A semiconductor device 300 is made by using the screen printing means. The semiconductor device 300 comprises a semiconductor element 310 mounted face down on the top surface of a substrate 311. Top face and side face of the semiconductor element 310 are covered with a coating film 312. The semiconductor element 310 is electrically connected with a lead electrode 315 that is formed on the substrate 311. The semiconductor device 300 is made by providing a side wall 316 that serves as a mask having a predetermined shape, spreading a resin 313 with a squeegee 314, thereby forming the coating film 312 on the top face of the semiconductor element 310. After forming the coating film 312, the side wall 316 serving as a mask is removed, thus having the coating film 312 formed on the top face and side face of the semiconductor element 310.
However, the semiconductor device 200 made by using the conventional potting means and the semiconductor device 500 made by using the conventional screen printing means have problems as described below.
In the semiconductor device 200 made by using the conventional potting means, the coating film 212 that covers the top face and side face of the semiconductor element 210 cannot be formed with uniform thickness. For example, when a semiconductor light emitting element is used as the semiconductor element 210 and a fluorescent material is mixed in the coating film 212, difference in thickness of the film among products results in variability in color between products as light emitted by the semiconductor light emitting element is absorbed by the fluorescent material and light of different wavelength generated by the fluorescent material is emitted to the outside. In addition, since the coating film is thicker in the portion where resin 213 has been dropped from the thin tube 214 and thinner in the surrounding portion, larger amount of light emitted by the fluorescent material 6 emerges from the potted portion, while smaller amount of light emitted by the fluorescent material 6 emerges from the surrounding portion, thus resulting in color unevenness.
In the semiconductor device 300 made by using the conventional screen printing means, it is difficult to form the coating film 312 that covers the top face and the side face of the semiconductor element 310 with uniform thickness. It is also difficult to manufacture, as the coating film 312 may come off along with the side wall 316 that makes the mask when the side wall 316 is removed from the coating film 312.